This invention relates to a method and apparatus for measuring charged ion concentrations of biological organisms, particularly, in humans.
It is known that a large number of hydrogen atoms are present in bio-organic compounds. Normal blood plasma consists of protein, salt, water, albumin, sugar and urea, having hydrogen (H+) ion concentration of approximately 0.4.times.10.sup.-7 gr/liter. This corresponds to a pH equal to 7.4. The blood is highly buffered due to its interaction with sodium bicarbonate, thus, yielding a narrow pH range that is typically characteristic of humans.
Measurement of resistance or conductivity can be made by various means by which electrical fields are induced and vectorially measured to determine their magnitude. Presently, there are a number of such devices but none can truly distinguish between ground current loops, variation in capacitance and a living organism.
This application disclosed an improvement in the method of detection of conductive bodies specifically directed toward a specified range of measurement, comparable to pH of 7.1 to 7.8. In comparisonpresent state of the art devices, sensors are used for detecting metal objects comprised of an oscillator, coils and a balancingelectronic bridge which nulls a signal in the absence of metal.
A more sophisticated system provides orthogonal signals in a phase correlated configuration that allows discrimination of various metals and/or ranges of conductivities. These devices when applied for human detection do not work or are inaccurate, have a high range of failure and are quite expensive. Similar to the above are those systems that necessitate radioactive substances for ionization paths between the organism and the apparatus.
The desirability of contact or contactless systems for detecting and measuring the pH in biological organisms is recognized. Nuclear Magnetic Resonance Imaging in Medicine, Leon Kaufman, et. al., IGAKO-SHOIN, Publication, N.Y. (1944).; NMR Imaging in Biomedicine, Supplement 2, P. Manfield, et. al., Academic Press (1982). From the publications it is clear that such measurements are accomplished by measuring the phosphorus nuclei, a difficult and expensiveprocess. Patents related to such systems are Hoogendoorn, et. al., U.S. Pat. No. 4,602,639 issued June, 1986; Mee, et al. U.S. Pat. No. 4,578,635, issued March, 1986; Lerman, U.S. Pat. No. 4,574,810, issued March, 1986; Stoller, et. al., U.S. Pat. No. 4,557,271, issued December, 1985; Atlas, U.S. Pat. No. 4,540,002, issued September, 1985; Conners, et. al., U.S. Pat. No. 4,459,995, issued July, 1984; Briggs, U.S. Pat. No. 4,300,574, issued November, 1981. Of these patents the most pertinent is Hoogendoorn, et. al. which deals primarily with capacitive measurements, while all the other patents cited deal with a basic resistance measuring in Ohn factors in a living body. The present invention proposes substantial improvements in such devices than those disclosed in the cited patents.